Sporadic occurrence of non-diagnosed IgG4-related disease in lymphoma patients with a previous Sjögren’s syndrome diagnosis

<p><b>Background:</b> IgG4-related disease (IgG4-RD) is a recently recognized fibro-inflammatory disorder, which may affect many organs, and often comes to clinical attention due to tumor-like organ swelling or is identified incidentally by specific biopsy findings. Typical histopathology of IgG4-RD is lymphoplasmacytic infiltration rich in IgG4 + plasma cells (PCs), storiform fibrosis, and obliterative phlebitis. Patients with sicca symptoms can be misdiagnosed as primary Sjögren’s syndrome (pSS) instead of IgG4-RD because of clinical and histopathological similarities. Moreover, an association with lymphoma development is described in both diseases. This study investigated signs of IgG4-RD in a population-based cohort of patients diagnosed with pSS complicated by lymphoma.</p> <p><b>Methods:</b> Patients with pSS and lymphoma diagnoses and available lymphoma specimens were identified by linkage with the Swedish Patient Register 1964–2007 and the Cancer Register 1990–2007 (n = 79). Clinical data and lymphomas were reviewed and the diagnoses evaluated. All lymphoma tissues and available minor salivary gland biopsies (n = 11) were immunostained for IgG4 + PCs and evaluated for other histopathological signs of IgG4-RD. In a case with specific findings of IgG4-RD, other available tissue specimens of the same patient were investigated for IgG4-RD.</p> <p><b>Results:</b> Only one patient of 79 (1.3%) had >10 IgG4 + PCs/high power field (HPF) in the lymphoma tissue, an unspecified low-grade B-cell lymphoma localized in the submandibular gland. This patient also had other histopathological features of IgG4-RD in the lymphoma and a surgical lung biopsy taken five years before lymphoma diagnosis and, therefore, fulfilled the criteria for IgG4-RD. Occasional IgG4 + PCs (<10/HPF) without signs of IgG4-RD were observed in another six lymphomas. No IgG4 + PCs were identified in the minor salivary gland biopsies.</p> <p><b>Conclusion:</b> Histopathological findings of IgG4-RD may co-exist with low malignant B-cell lymphoma in patients with initially suspected pSS and may be associated with an underlying IgG4-RD.</p

Tissue samples included for RNA expression profiling.

<p>The estimated percentages of cells are given for each tissue type. In bone marrow, cells of erythropoietic origin are mostly immature and nucleated precursors. * In secondary lymphoid organs, fully maturated erythrocytes are not included, since they are unlikely to contribute to the transcriptomic profile. ** Other cell types refer to adipocytes, fibroblasts, smooth muscle cells and glandular cells.</p><p>Tissue samples included for RNA expression profiling.</p

Summary of transcriptomic profiling of lymphohematopoietic tissues.

<p>Summary of transcriptomic profiling of lymphohematopoietic tissues.</p

Immunohistochemical staining of protein expression.

<p>The staining patterns of 19 proteins transcribed from genes in the enriched or enhanced categories are exemplified here in one to three tissue types. The gene name, tissue type and FPKM-value in brackets are shown for each image. BM: bone marrow; LN: lymph node; Appx: appendix.</p

Classification of gene expression patterns as determined over 27 tissues.

<p>Classification of gene expression patterns as determined over 27 tissues.</p

Network plot visualizing the relationship of enriched genes in the lymphohematopoietic tissues.

<p>a) Dark blue nodes represent genes that are group enriched in up to five different tissue types including at least one of the lymphohematopoietic tissues. The light blue nodes represent the total number of highly and moderately tissue enriched genes in each lymphohematopoietic tissue. The size of each blue (dark and light) node is related to the square root of the number of genes within. Black circles represent the four lymphohematopoietic tissues, and grey circles denote other tissue types. b) Names of enriched genes (and enhanced genes in brackets) that are exemplified in the text and shown in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115911#pone-0115911-g004" target="_blank">Fig. 4</a>. The color codes are equal to the nodes in a). The network plot is limited to include nodes with a minimum of two genes.</p

Pie charts displaying the expression profiles for the lymphohematopoietic tissues.

<p>The upper panel shows the percentage of genes expressed within the different categories of expression, for bone marrow and for the secondary lymphoid organs respectively. The lower panel pie charts show the percentage of transcripts (FPKM) for each category.</p

Dendrogram and correlation plots for the lymphohematopoietic tissues.

<p>a) Dendrogram covering all samples of the four lymphohematopoietic tissue types visualizing clustering according to gene expression profiles. Correlation plots are shown for b) spleen and bone marrow displaying the lowest correlation between the four lymphohematopoietic tissues, and for c) lymph node and appendix displaying the highest correlation, based on the average FPKM-value of all samples within the same tissue type (n = 3–5).</p

Immunoreactive (IR) grains in the tumour cells, seen upon the application of the late human cytomegalovirus tegument protein antibody pp65 (clones 2 and 6) in f-j.

<p>Identification of cell type was carried out applying cell type specific antibodies (Ab) – a) membranous labelling of oligodendrocytes with Ab directed to microtubule associated protein 2 (MAP2); b) cytoplasmic labelling of astrocytes with Ab directed to glial fibrillary acidic protein (GFAP); c) granular cytoplasmic labelling of neuronal cells with Ab directed to synaptophysin (SYP); d) membranous labelling of lymphocytes with Ab directed to B-lymphocyte antigen CD20 (CD20) and e) cytoplasmic labelling of meningothelial cells with Ab directed to epithelial membrane antigen (EMA). HCMV-IR grains seen in all tumour types (f-j), few pp65-IR granules in the ologodendroglioma and lymphoma samples (arrows on f and i) and numerous granules in glioblastoma, medulloblastoma and meningioma (g, h, j). In k-o cases lacking HCMV-IR. Magnification x400.</p

Expression of cytomegalovirus protein pp65 in the included extra and intra axial brain tumors.

<p>HCMV- human cytomegalovirus, superscript- number of not assessable cases, subscript – number of assessed cases in the group.</p><p>Expression of cytomegalovirus protein pp65 in the included extra and intra axial brain tumors.</p